Viscosifier for oil base drilling fluids

Abstract

A viscosifier for an oil base drilling fluid of the type used in well drilling and workover procedures is shown which comprises an effective amount of a montan wax dispersed within the fluid to provide the needed viscosity and gel strength to properly suspend solids in the drilling fluid. Montan wax is dispersed in an oil base which contains as little as about 5 volume percent water. A basic material, such as lime, reacts in the water with the montan wax, and the partial saponification which results produces a thixotropic drilling fluid.

I claim: 
     
       1. An oil base drilling fluid composition, comprising: an oil base fluid present in the range of about 95 to 75 percent by volume of the drilling fluid composition;   montan wax having a melting point in the range of about 76° to 120° and an acid number and a saponification number greater than about 100, said montan wax being present in the range from about 5 to 20 pounds per barrel of drilling fluid composition;   a basic material selected from the group consisting of diethanolamine, alkali metal hydroxides, alkaline earth oxides, and alkaline earth hydroxides capable of forming a soap with said montan wax;   water present in the range of about 5 to 25 percent by volume of the drilling fluid composition; and   said oil base drilling fluid composition being characterized by the substantial absence of any dispersed asphalt.   
     
     
       2. An oil base drilling fluid composition, comprising: an oil base fluid present in the range of about 95 to 75 percent by volume of the drilling fluid composition;   montan wax having a melting point in the range of about 76° to 120° C. and an acid number and a saponification number greater than about 100, said montan wax being present in the range from about 5 to 20 pounds per barrel of drilling fluid composition;   a basic material selected from the group consisting of diethanolamine, alkali metal hydroxides, alkaline earth oxides, and alkaline earth hydroxides capable of forming a soap with montan wax;   water present in the range of about 5 to 25 percent by volume of the drilling fluid composition; and   an emulsifying additive, said oil base drilling fluid composition being characterized by the substantial absence of any dispersed asphalt.   
     
     
       3. The oil base drilling fluid composition of claim 2, wherein said basic material is lime. 
     
     
       4. The oil base drilling fluid composition of claim 3, wherein said basic material is present in the range of about 2 to 10 pounds per barrel of drilling fluid composition. 
     
     
       5. The oil base drilling fluid composition of claim 4, wherein said water is present as a saturated brine solution containing 300,000 to 350,000 ppm calcium chloride. 
     
     
       6. An oil base drilling fluid composition having a low solids content for well completion and workover operations, comprising: an oil base fluid present in the range of about 95 to 75 percent by volume of the drilling fluid composition;   a montan wax having a melting point in the range of about 76°-120° C. and an acid number and a saponification number greater than about 100, said wax being present in the range of about 5 to 20 pounds per barrel of drilling fluid composition;   lime as a basic material capable of forming a soap with said montan wax, said lime being present in the range of about 2 to 10 pounds per barrel of drilling fluid composition;   brine, present in the range of about 5 to 25 percent by volume of the drilling fluid composition, said brine containing 250,000-300,000 ppm calcium chloride salt;   an emulsifying additive; and   pentaerythritol, said oil base drilling fluid composition being characterized by the substantial absence of any dispersed asphalt.